linux-kernel - Re: [PATCH v1 3/3] LoongArch: Fix unreachable instruction warnings about entry functions

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Message-ID: <ots6w2ntyudj5ucs5eowncta2vmfssatpcqwzpar3ekk577hxi@j45dd4dmwx6x>
Date: Wed, 3 Sep 2025 12:22:19 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Tiezhu Yang <yangtiezhu@...ngson.cn>
Cc: Huacai Chen <chenhuacai@...nel.org>, 
	Peter Zijlstra <peterz@...radead.org>, Nathan Chancellor <nathan@...nel.org>, loongarch@...ts.linux.dev, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 3/3] LoongArch: Fix unreachable instruction warnings
 about entry functions

On Mon, Sep 01, 2025 at 03:21:56PM +0800, Tiezhu Yang wrote:
> +++ b/arch/loongarch/kernel/Makefile
> @@ -3,8 +3,6 @@
>  # Makefile for the Linux/LoongArch kernel.
>  #
>  
> -OBJECT_FILES_NON_STANDARD_head.o := y
> -
>  always-$(KBUILD_BUILTIN)	:= vmlinux.lds
>  
>  obj-y		+= head.o cpu-probe.o cacheinfo.o env.o setup.o entry.o genex.o \
> diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
> index e3865e92a917..a11880f3a7e1 100644
> --- a/arch/loongarch/kernel/head.S
> +++ b/arch/loongarch/kernel/head.S
> @@ -42,6 +42,7 @@ SYM_DATA(kernel_fsize, .long _kernel_fsize);
>  	.align 12
>  
>  SYM_CODE_START(kernel_entry)			# kernel entry point
> +	UNWIND_HINT_UNDEFINED

Should this not be UNWIND_HINT_END_OF_STACK?

I notice Loongarch doesn't seem to use that anywhere.  How does any ORC
unwind succeed?  UNWIND_HINT_UNDEFINED sets an error condition which
should cause a livepatch transition to stall.

-- 
Josh